Fifteen months after the murders, Sgt Lewis was also picked out of a line-up by Nicola Williams.

But he was released without charge after his wife Alison told police he had been with her all night.

His brother Inspector Stuart Lewis was initially questioned, but has never been questioned or investigated as a murder suspect in the case.

He was questioned about his movements - on suspicion of perverting the course of justice - a year later, when his brother was arrested.

Inspector Stuart Lewis faced no charges. He has never been confronted about the e-fit.

But he does believe he should have been brought in for questioning as soon as the e-fit was released a week after the murders.

While being secretly filmed for the programme, Inspector Stuart Lewis admitted the likeness, saying: "When I saw that photo fit, basically I remember looking at it and thinking, Jesus Christ, look at that.

Distorted photo

Inspector Stuart Lewis was surprised he wasn't arrested in connection with the case

"The question you should be asking is, why wasn't anything done about that? I mean when I saw it, I was amazed."

Panorama has also discovered that in a pre-trial hearing, the trial judge saw a photo montage which showed the e-fit picture with a photo of Sgt Lewis next to it.

Forensics expert Ashley Windsor was asked by Panorama to examine the photos.

He has come to the conclusion the photo of Sgt Lewis was distorted.

He said: "It's very significant because the faces look completely different and I know this one is not a true representation of how the person looked."